Adequate parental care of neonates is an indispensable component of successful reproduction in most mammals. However, compared with other behaviors necessary for mammalian reproduction, relatively little is known about the neural pathways underlying parental behavior. This application addresses this issue by investigating the neurochemical substrates regulating maternal care in lactating rats. The main objective is to determine the role of dopaminergic pathways to the medial preoptic area (mPOA) in these behaviors. The mPOA is necessary for some oral components of maternal behavior in rats, such as retrieval of pups, and plays a role in the motivation to act parentally. However, the neurochemical pathways to and from the mPOA underlying these aspects of maternal behavior are completely unknown. It is probable that the hormones of gestation and parturition, as well as sensory cues from pups that dams receive after parturition, influence neurochemical release in the mPOA in a way that promotes maternal performance. One neurochemical in the mPOA that may be necessary for maternal behavior is dopamine. The mPOA has not been one of the neural sites previously examined as a place where dopamine release is necessary for maternal behavior, but this may be a distinct possibility because dopamine release in the mPOA is necessary for other behavioral and motivational aspects of reproduction in rats. It is proposed that dopamine release within the mPOA is necessary for the onset of maternal behavior at parturition as well as for the performance of ongoing maternal behavior in lactating rats. Specific Aim 1 will use high performance liquid chromatography (HPLC) to examine changes that occur in dopaminergic content within the mPOA of female rats during the reproductive cycle and during postpartum interactions with pups. Specific Aim 2 will use retrograde neuroanatomical tracing combined with fluorescence immunocytochemistry for tyrosine hydroxylase, the rate-limiting enzyme necessary for catecholamine synthesis, to determine the source of dopaminergic and other catecholaminergic pathways to the mPOA in virgin and lactating female rats. Specific Aim 3 will examine the effects of pre- or postpartum 6-hydroxydopamine (6-OHDA) lesions of the dopaminergic terminals in the mPOA on the onset and maintenance of maternal behavior in lactating rats. Specific Aim 4 will determine the effects of pharmacological antagonism of specific dopamine receptor subtypes within the mPOA on postpartum maternal behavior in lactating rats. These results will provide much needed insight into how the brain controls nurturant behavior, which is a complex social behavior that is often critical for survival in many mammalian species.